scholarly journals Rock Location and Property Analysis of Lunar Regolith at Chang’E-4 Landing Site Based on Local Correlation and Semblance Analysis

2020 ◽  
Vol 13 (1) ◽  
pp. 48
Author(s):  
Hanjie Song ◽  
Chao Li ◽  
Jinhai Zhang ◽  
Xing Wu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Lunar Regolith ◽  
Landing Site ◽  
Rock Properties ◽  
The Moon ◽  
Local Correlation ◽  
Near Surface ◽  
Property Analysis ◽  
Stratigraphic Division ◽  
Formation And Evolution

The Lunar Penetrating Radar (LPR) onboard the Yutu-2 rover from China’s Chang’E-4 (CE-4) mission is used to probe the subsurface structure and the near-surface stratigraphic structure of the lunar regolith on the farside of the Moon. Structural analysis of regolith could provide abundant information on the formation and evolution of the Moon, in which the rock location and property analysis are the key procedures during the interpretation of LPR data. The subsurface velocity of electromagnetic waves is a vital parameter for stratigraphic division, rock location estimates, and calculating the rock properties in the interpretation of LPR data. In this paper, we propose a procedure that combines the regolith rock extraction technique based on local correlation between the two sets of LPR high-frequency channel data and the common offset semblance analysis to determine the velocity from LPR diffraction hyperbola. We consider the heterogeneity of the regolith and derive the relative permittivity distribution based on the rock extraction and semblance analysis. The numerical simulation results show that the procedure is able to obtain the high-precision position and properties of the rock. Furthermore, we apply this procedure to CE-4 LPR data and obtain preferable estimations of the rock locations and the properties of the lunar subsurface regolith.

scholarly journals Rock Location and Quantitative Analysis of Regolith at the Chang’e 3 Landing Site Based on Local Similarity Constraint

2019 ◽  
Vol 11 (5) ◽  
pp. 530 ◽  
Author(s):  
Bin Hu ◽  
Deli Wang ◽  
Ling Zhang ◽  
Zhaofa Zeng
Keyword(s):  
Quantitative Analysis ◽  
Lunar Regolith ◽  
Landing Site ◽  
Threshold Function ◽  
Local Similarity ◽  
Near Surface ◽  
Processing Pipeline ◽  
Mode Decomposition ◽  
Lunar Geology ◽  
The One

Structural analysis of lunar regolith not only provides important information about lunar geology but also provides a reference for future lunar sample return missions. The Lunar Penetrating Radar (LPR) onboard China’s Chang’E-3 (CE-3) provides a unique opportunity for mapping the subsurface structure and the near-surface stratigraphic structure of the regolith. The problem of rock positioning and regolith-basement interface highlighting is meaningful. In this paper, we propose an adaptive rock extraction method based on local similarity constraints to achieve the rock location and quantitative analysis for regolith. Firstly, a processing pipeline is designed to image the LPR CH-2 A and B data. Secondly, we adopt an f-x EMD (empirical mode decomposition)-based dip filter to extract low-wavenumber components in the two data. Then, we calculate the local similarity spectrum between the filtered CH-2 A and B. After a soft threshold function, we pick the local maximums in the spectrum as the location of each rock. Finally, according to the extracted result, on the one hand, the depth of regolith is obtained, and on the other hand, the distribution information of the rocks in regolith, which changes with the path and the depth, is also revealed.

scholarly journals Weak Signal Extraction from Lunar Penetrating Radar Channel 1 Data Based on Local Correlation

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 573 ◽  
Author(s):  
Zhuo Jia ◽  
Sixin Liu ◽  
Ling Zhang ◽  
Bin Hu ◽  
Jianmin Zhang
Keyword(s):  
Signal To Noise Ratio ◽  
Lunar Regolith ◽  
Signal Extraction ◽  
Weak Signal ◽  
Human Beings ◽  
Subsurface Structure ◽  
Local Correlation ◽  
Signal To Noise ◽  
Near Surface ◽  
Noise Ratio

Knowledge of the subsurface structure not only provides useful information on lunar geology, but it also can quantify the potential lunar resources for human beings. The dual-frequency lunar penetrating radar (LPR) aboard the Yutu rover offers a Special opportunity to understand the subsurface structure to a depth of several hundreds of meters using a low-frequency channel (channel 1), as well as layer near-surface stratigraphic structure of the regolith using high-frequency observations (channel 2). The channel 1 data of the LPR has a very low signal-to-noise ratio. However, the extraction of weak signals from the data represents a problem worth exploring. In this article, we propose a weak signal extraction method in view of local correlation to analyze the LPR CH-1 data, to facilitate a study of the lunar regolith structure. First, we build a pre-processing workflow to increase the signal-to-noise ratio (SNR). Second, we apply the K-L transform to separate the horizontal signal and then use the seislet transform (ST) to reserve the continuous signal. Then, the local correlation map is calculated using the two denoising results and a time–space dependent weighting operator is constructed to suppress the noise residuals. The weak signal after noise suppression may provide a new reference for subsequent data interpretation. Finally, in combination with the regional geology and previous research, we provide some speculative interpretations of the LPR CH-1 data.

scholarly journals Parameter Estimation of Lunar Regolith from Lunar Penetrating Radar Data

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2907 ◽  
Author(s):  
Ling Zhang ◽  
Zhaofa Zeng ◽  
Jing Li ◽  
Ling Huang ◽  
Zhijun Huo ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Parameter Estimation ◽  
Lunar Regolith ◽  
Relative Dielectric Constant ◽  
Landing Site ◽  
Radar Data ◽  
Titanium Content ◽  
Complex Model ◽  
Electrical Parameters ◽  
Near Surface

Parameter estimation of the lunar regolith not only provides important information about the composition but is also critical to quantifying potential resources for lunar exploration and engineering for human outposts. The Lunar Penetrating Radar (LPR) onboard China’s Chang’E-3 (CE-3) provides a unique opportunity for mapping the near-surface stratigraphic structure and estimating the parameters of the regolith. In this paper, the electrical parameters and the iron-titanium content of regolith are estimated based on the two sets of LPR data. Firstly, it is theoretically verified that the relative dielectric constant can be estimated according to the difference of the reflected time of two receivers from a same target. Secondly, in order to verify the method, a parameter estimation flow is designed. Subsequently, a simple model and a complex model of regolith are carried out for the method verification. Finally, on the basis of the two sets of LPR data, the electrical parameters and the iron-titanium content of regolith are estimated. The relative dielectric constant of regolith at CE-3 landing site is 3.0537 and the content of TiO2 and FeO is 14.0127%. This helps us predict the reserves of resources at the CE-3 landing site and even in the entire Mare Imbrium.

Lunar Dust

2020 ◽  
Author(s):  
Alexander V. Zakharov
Keyword(s):  
Solar Wind ◽  
Solar Radiation ◽  
Lunar Surface ◽  
Lunar Regolith ◽  
Dust Particles ◽  
The Moon ◽  
Near Surface ◽  
Lunar Dust ◽  
Research Programs ◽  
The Impact

The surface of the Moon, as well as the surface of an airless body of the solar system, is subject to constant bombardment of micrometeorites, the effects of solar radiation, solar wind, and other space factors. As a result of the impact of high-speed micrometeorites for billions of years, the silicate base of the lunar surface is crushed, turning into particles with an approximately power-law-sized distribution. Given the explosive nature of the occurrence, these particles are characterized by an extremely irregular shape with pointed edges, either droplets close to spheres or conglomerates sintered at high temperatures. The plasma of the solar wind and the solar radiation, especially its ultraviolet part of the spectrum, when interacting with the upper layer of regolith causes a charge of the regolith upper layer and creates a near-surface double layer and an electric field. In this field, regolith particles of micron and submicron sizes can break away from the surface and levitate above the surface. Such dynamic processes lead to the transfer of dust particles over the surface of the Moon, as well as to the scattering of sunlight on these particles. Glows above the lunar surface of this nature were observed by television systems of American and Soviet landers in the early stages of lunar exploration. The American astronauts who landed on the lunar surface during the Apollo program experienced the aggressive properties of lunar dust. The results of the Apollo missions showed that dust particles are one of the main causes of danger to humans, spacecraft systems, and activities on the lunar surface. Based on the results of late 20th- and early 21st-century lunar research, as well as the proposed models, the article discusses the formation of the lunar regolith and the near-surface exosphere of the Moon under the influence of external factors in outer space. Relevant considerations include the causes and conditions of dust particle dynamics, the consequences of these processes as well as possible threats to humans, engineering systems during the implementation of planned research programs, and the exploration of the Moon. Also of relevance are models of the formation of a plasma-dust exosphere, the dynamics of dust particles in the near-surface region, and dust clouds at a distance of several tens of kilometers from the Moon’s surface, based on the available experimental data. The main unresolved problems associated with the dynamics of the dust component of lunar regolith are given, and methods for solving problematic issues are discussed. The Moon research programs of leading space agencies and their role in the study of Moon dust, its dynamics, human impact, and its activities in the implementation of promising programs for the study and exploration of the Moon are examined.

scholarly journals Properties Analysis of Lunar Regolith at Chang’E-4 Landing Site Based on 3D Velocity Spectrum of Lunar Penetrating Radar

2020 ◽  
Vol 12 (4) ◽  
pp. 629 ◽  
Author(s):  
Zejun Dong ◽  
Xuan Feng ◽  
Haoqiu Zhou ◽  
Cai Liu ◽  
Zhaofa Zeng ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Lunar Regolith ◽  
Landing Site ◽  
Threshold Function ◽  
Velocity Spectrum ◽  
Maximum Relative Error ◽  
Soft Landing ◽  
Average Maximum ◽  
Effective Instrument ◽  
Moon Exploration

The Chinese Chang’E-4 mission for moon exploration has been successfully completed. The Chang’E-4 probe achieved the first-ever soft landing on the floor of Von Kármán crater (177.59°E, 45.46°S) of the South Pole-Aitken (SPA) basin on January 3, 2019. Yutu-2 rover is mounted with several scientific instruments including a lunar penetrating radar (LPR), which is an effective instrument to detect the lunar subsurface structure. During the interpretation of LPR data, subsurface velocity of electromagnetic waves is a vital parameter necessary for stratigraphic division and computing other properties. However, the methods in previous research on Chang’E-3 cannot perform velocity analysis automatically and objectively. In this paper, the 3D velocity spectrum is applied to property analysis of LPR data from Chang’E-4. The result shows that 3D velocity spectrum can automatically search for hyperbolas; the maximum value at velocity axis with a soft threshold function can provide the horizontal position, two-way reflected time and velocity of each hyperbola; the average maximum relative error of velocity is estimated to be 7.99%. Based on the estimated velocities of 30 hyperbolas, the structures of subsurface properties are obtained, including velocity, relative permittivity, density, and content of FeO and TiO2.

scholarly journals Photometric properties of lunar regolith revealed by the Yutu-2 rover

2020 ◽  
Vol 638 ◽  
pp. A35 ◽  
Author(s):  
Honglei Lin ◽  
Yazhou Yang ◽  
Yangting Lin ◽  
Yang Liu ◽  
Yong Wei ◽  
...  
Keyword(s):  
Near Infrared ◽  
Surface Composition ◽  
Lunar Regolith ◽  
Remote Sensing Data ◽  
Landing Site ◽  
Ground Truth ◽  
Wavelength Dependence ◽  
Forward Scattering ◽  
Small Scale ◽  
The Moon

Context. The surface composition of the Moon has mainly determined based on the visible and near-infrared spectra achieved from orbits and/or landing sites, and the spectroscopic analysis is based on photometric properties of the topmost lunar regolith. However, the lack of a ground truth for the photometric parameters of the undisturbed lunar surface has limited accurate applications of spectral observations. Aims. Here we report the photometric properties of the small-scale (i.e., centimeter level) undisturbed lunar regolith around the Chang’E-4 landing site, determined from a series of photometric experiments conducted by the rover Yutu-2. Methods. The simplified Hapke model was used to derive the photometric properties. The micro-topographic effect on the spectral measurements was corrected for the first time in the in situ photometric investigations on the Moon, which improves the accuracy of the derived photometric parameters. Results. The single-scattering albedo w and two parameters (b, c) of the Henyey-Greenstein phase function were derived, and they show a wavelength dependence. The regolith at the Chang’E-4 landing site exhibits strong forward scattering according to the retrieved c values, and the higher asymmetry parameter indicates that the regolith here is more strongly forward scattering than the Apollo lunar soil samples. The derived photometric parameters can serve as ground truth and can be used in the radiative transfer modeling analysis of the orbital remote-sensing data.

Field tests of electroseismic hydrocarbon detection

Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. N1-N9 ◽  
Author(s):  
A. H. Thompson ◽  
Scott Hornbostel ◽  
Jim Burns ◽  
Tom Murray ◽  
Robert Raschke ◽  
...  
Keyword(s):  
Electric Fields ◽  
Electromagnetic Waves ◽  
Field Tests ◽  
Oil Reservoirs ◽  
Rock Properties ◽  
Near Surface ◽  
Hydrocarbon Detection ◽  
Wave Conversion ◽  
Seismic Coupling ◽  
Surface Generate

Geophysicists, looking for new exploration tools, have studied the coupling between seismic and electromagnetic waves in the near-surface since the 1930s. Our research explores the possibility that electromagnetic-to-seismic (ES) conversion is useful at greater depths. Field tests of ES conversion over gas sands and carbonate oil reservoirs succeeded in delineating known hydrocarbon accumulations from depths up to [Formula: see text]. This is the first observation of electromagnetic-to-seismic coupling from surface electrodes and geophones. Electrodes at the earth’s surface generate electric fields at the target and digital accelerometers detect the returning seismic wave. Conversion at depth is confirmed with hydrophones placed in wells. The gas sands yielded a linear ES response, as expected for electrokinetic energy conversion, and in qualitative agreement with numerical simulations. The carbonate oil reservoirs generate nonlinear conversions; a qualitatively new observation and a new probe of rock properties. The hard-rock results suggest applications in lithologies where seismic hydrocarbon indicators are weak. With greater effort, deeper penetration should be possible.

scholarly journals Near-surface real-time seismic imaging using parsimonious interferometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sherif M. Hanafy ◽  
Hussein Hoteit ◽  
Jing Li ◽  
Gerard T. Schuster
Keyword(s):  
Fluid Flow ◽  
Real Time ◽  
Temporal Resolution ◽  
Seismic Imaging ◽  
Time Lapse ◽  
Rock Properties ◽  
Recording Time ◽  
Near Surface ◽  
Arrival Times ◽  
Order Of Magnitude

AbstractResults are presented for real-time seismic imaging of subsurface fluid flow by parsimonious refraction and surface-wave interferometry. Each subsurface velocity image inverted from time-lapse seismic data only requires several minutes of recording time, which is less than the time-scale of the fluid-induced changes in the rock properties. In this sense this is real-time imaging. The images are P-velocity tomograms inverted from the first-arrival times and the S-velocity tomograms inverted from dispersion curves. Compared to conventional seismic imaging, parsimonious interferometry reduces the recording time and increases the temporal resolution of time-lapse seismic images by more than an order-of-magnitude. In our seismic experiment, we recorded 90 sparse data sets over 4.5 h while injecting 12-tons of water into a sand dune. Results show that the percolation of water is mostly along layered boundaries down to a depth of a few meters, which is consistent with our 3D computational fluid flow simulations and laboratory experiments. The significance of parsimonious interferometry is that it provides more than an order-of-magnitude increase of temporal resolution in time-lapse seismic imaging. We believe that real-time seismic imaging will have important applications for non-destructive characterization in environmental, biomedical, and subsurface imaging.

Anomalous Dielectric Variability in the central peak of Tycho crater on the Moon: New insights from Mini-RF S-band Observations

2021 ◽  
Author(s):  
Shashwat Shukla ◽  
Gerald Wesley Patterson
Keyword(s):  
Dielectric Constant ◽  
Hyperspectral Image ◽  
Central Peak ◽  
Skin Depth ◽  
The Moon ◽  
Near Surface ◽  
Low Dielectric ◽  
Crater Morphology ◽  
High Dielectric ◽  
The Impact

<p>One of the unique candidates to explore the evolution of physical surface processes on the Moon is Tycho, a dark haloed impact crater representing well-preserved bright ray pattern and intact crater morphology. Sampling of the central peak in such complex crater formation proves significant in terms of unraveling intriguing science of the lunar interior. With the current state-of-the-art radar technology, it is possible to evaluate the response of the geologic features constrained in the near surface and subsurface regolith environments. This can be achieved by modelling the dielectric constant of media, which is a physical parameter crucial for furthering our knowledge about the distribution of materials within different stratigraphic layers at multiple depths. Here, we used the applicability of Mini-RF S-band data augmented with a deep learning based inversion model to retrieve the dielectric variations over the central peak of the Tycho crater. A striking observation is made in certain regions of the central peak, wherein we observe anomalously high dielectric constant, not at all differentiated in the hyperspectral image and first Stokes parameter image, which usually is a representation of retrieved backscatter of the target. The results are also supported by comparing the variations in the scattering mechanisms. We found those particular regions to be associated with high degree of depolarization, thereby attributing to the presence of cm- to m- scale scatterers buried within a low dielectric layer that are not big enough to produce even-bounce geometry for the radar wave. Moreover, we also observe high rock concentration in the central peak slopes from DIVINER data and NAC images, indicating the exposure of clasts ranging in size from 10 meter to 100s of meter. Furthermore, from surface temperature data, these distinctive outcrops sense warmer temperature at night than the surrounding, which suggests the existence of thermal skin depth in such vicinities. Interestingly, we are able to quantify the pessimistic dielectric constant limit of the large boulder in the middle of the central peak, observable at the Mini-RF radar wavelength, as 4.54 + j0.077. Compared to the expected dielectric constant of rocks, this value is lowered significantly. One probable reason could be the emergence of small radar shadows due to the rugged surface of the boulder on the radar illuminated portion. From our analysis, we showcase the anomalous dielectric variability of Tycho central peak, thereby providing new insights into the evolution of the impact cratering process that could be important for both science and necessary for framing human or robotic exploration strategies.  </p>

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